(a) Field of the Invention
The present invention relates to a method of and an apparatus for removing of sea-growth, such as barnacles, weeds, etc., from marine objects, and in particular to the removal of sea-growth from the submerged hull surfaces of ships or the like.
(B) Descripton of the Prior Art
All sea-going ships have to be cleaned periodically, for a minimum of once every 2 years up to as many as three or four times a year. Navy ships, and in particular submarines, may require cleaning every 3 months in order to maintain their operating efficiency. The regularity of cleaning is predicated on the marine life growth factor in the particular area in which the ship is operating. Various crustaceans and sea moss growth slow a vessel's speed anywhere between a half knot up to two knots. Of course, such a reduction in speed causes an economic loss.
The present state of the art still maintains a physical removal process by scraping, sandblasting, or some other scratching process which is normally performed in dry docks. Apart from the cost of dry docking, the abrasive process destroys any remaining anti-fouling paint layers on the hull and these, which might otherwise last for a substantial time, have to be reapplied. A typical scraping machine is shown in U.S. Pat. No. 2,104,062 by Temple.
A different and more sophisticated ship's cleaning device has been disclosed in U.S. Pat. No. 3,068,829 by Nuissl which improved the art of cleaning a ship's hull without putting the ship into a dry dock. The cleaning process is performed by an ultrasonic frequency supplied by an apparatus that travels along the ship's hull and is steered by divers. However, a cleaning process of this type covers a very small area of the hull only and is therefore time consuming. Also, the physical size of such a device and its power requirements might prove it to be impracticable.
In another development, a system is disclosed in U.S. Pat. No. 994,405 by James which would permanently keep the ship's hull free from the attaching of sea growths by providing high tension electricity in the vicinity of the submerged hull so as to impart a shock to animal or aquatic life whereby due to the high tension discharge a shock is imparted to such organisms and they are thereby prevented from attaching themselves. Thus, a permanently installed apparatus is disclosed which at regular intervals will electrocute the complete hull of a ship. This invention sounded correct at the time of disclosure. However, since sea water would act as an electrolyte in such a system, the resulting galvanic action associated with this system would consume sacrificial anode material at an impracticable rate.
In comparison to the present invention as disclosed hereinafter, it appears that the prior art has never been able to produce a workable, efficient system different from the first-mentioned abrasive or scraping system which is still used. The present invention uses accelerated seawater produced by an expanding gas-bubble pulse and a small amount of shock wave energy which produces a vibratory effect. The combination of these two energy effects when created in calculated controlled amounts will safely remove all sea-growth fouling in the area to it.
The prior art has taught systems utilizing explosives for cleaning purposes but these types of systems were never for cleaning submerged areas and utilized randomly unpredetermined set charges of explosives.
In general, it appears that the present invention provides for a new and improved method and apparatus to be used in the cleaning and/or removing of sea growth, such as barnacles, sea moss, etc., from the submerged areas of various marine objects such as ships, submarines, docks, bridges, pontoons, locks, etc., where such is desired. However, in particular the present invention claims and identifies a new and unique method for removing sea growth from submerged ship hulls more economically and faster than ever before.